The present invention relates to an antithrombogenic, non-calcifying, and elastic material on a basis of polyurethane and to a method of manufacturing articles for medical purposes that are appropriate for remaining in contact with human blood in both short-term and long-term use.
That polyurethanes are appropriate--due to such mechanical properties as elasticity, flexibility, tear-resistance, and to a certain extent antithrombogenicity--for the manufacture of such articles as prosthetic cardiac valves, coatings on cardiac-pacemaker electrodes, blood-storage bags, catheters, etc. is known. A long series of patents and patent applications (e.g. German patent No. 1 944 969, German OS No. 2 642 616, German OS No. 3 107 542, German OS No. 3 130 646, German OS No. 3 318 730, German OS No. 3 606 440, European patent No. 68 385, EPA No. 152 699, EPA No. 184 465, U.S. Pat. No. 4,350,806, U.S. Pat. No. 4,371,686, and U.S. Pat. No. 4,600,652) concerned with improving or optimizing the blood-compatibility in particular of the polyurethanes by means of additives or specially selected components have been published.
It has in the meantime, however, been shown that the blood compatibility of the materials, primarily their antithrombogenic action, is not the only critical point, but that calcification deposits and, in long-term application, biological breakdown are at least equivalent problems.
Washing what are called bioprostheses, which consist of natural tissue preferably cross-linked with glutaraldehyde, in an aqueous solution of alkyl sulfates (Eur. Pat. No. 65 827) or of water-soluble salts of alkylphosphorates like sodium dodecylhydrogen phosphate (U.S. Pat. No. 4,402,697) to prevent calcification is known. These methods, however, cannot be transferred to implants like polyurethane prosthetic cardiac valves because the salts do not attach to polyurethanes.